The long-term goal of the applicant is to be a successful independent scientist with a research program that focuses on virus-host interactions at the molecular level using tissue culture and mouse models of infection, with a particular interest in uncovering functions of viral proteins. Coronaviruses cause a variety of diseases in mammalian species. They have the potential to cause significant human morbidity and mortality as highlighted by the emergence of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and more recently the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). All Coronaviruses encode a highly conserved Macro domain within non-structural protein (nsp) 3 that makes it a useful therapeutic target. Macro domains are ADP-ribose (ADR) binding molecules conserved in eukaryotes and have diverse functions. The coronavirus Macro domain has phosphatase activity that converts ADP- ribose-1-phosphate (ADRP) into ADP-ribose (ADR). However, the role of this activity in viral replication or pathogenesis has remained a mystery. Using a mouse-adapted SARS-CoV (MA15), a Macro domain mutant virus was engineered and shown to replicate in tissue culture cells with wild-type kinetics. However, it is completely unable to cause lethal pneumonia in BALB/c mice and induces a large increase in specific pro-inflammatory cytokines compared to wild-type virus. The overall goal of this project is to determine the role for the Macro domain during SARS-CoV and other Coronavirus infections and determine why these viruses universally encode for this protein. Aim 1. We will identify the complete spectrum of cytokines that are differentially regulated during wild type and mutant virus infection using a broad range of methods including microarrays, qRT-PCR, and ELISAs. Active site Macro domain mutants in Murine Hepatitis Virus (MHV, a mouse model for coronavirus biology) and MERS-CoV will be engineered and used to expand our analyses to multiple cell types and coronavirus infection models. Aim 2. To identify the basis of upregulation of pro-inflammatory cytokines in cells infected with mutant virus, individual steps in their activation pathways will be analyzed. Additionally, purified ADRP will be used to test the intriguing possibility that ADRP may be a novel pathogen-associated molecular pattern (PAMP) that activates an innate immune response. Following completion of training, the applicant will be versed in tools needed to study the genetics, molecular biology, and pathogenesis of coronaviruses.